1. Field of the Invention
This invention relates generally to an apparatus and method for combing the operation of drilling a hole into a substrate workpiece and fusing a friction welding fitting onto that substrate in one set-up operation. The rotatable workpiece (stud, shaft or other type fitting) to be friction welded to a substrate workpiece, of either similar or dissimilar materials, or two circular shafts, can be friction welded together by use of an apparatus that can first drill a hole and then weld a fitting in place, in line with that hole. Friction welding, in general, is covered by prior art and it is envisioned that the invention disclosed herein could be adaptable to a wide range of friction welding apparatuses, since the apparatus disclosed herein could be adapted to many friction welder rotatable workpieces. This invention specifically relates to a friction welder drill and fuse fitting apparatus which can be utilized with a wide range of friction welder apparatuses, and methods for its use, although not limited to the geometric configurations provided herein.
2. Description of the Prior Art
One of the common industrial applications for fittings is the use of fittings on such industrial equipment "substrates" as tanks filled with liquid or gas, lines carrying liquid or gas, valves retrofitted for valve gland packing restoration, fire sprinkler system lines, plumbing lines, instrumentation fittings and other type fittings. These fittings could have multifaceted purposes, such as connecting other tanks and lines, instrumentation controls and readouts, valves, and other connecting apparatuses in both industrial and commercial applications. Fittings can be made from many different materials, depending on the strength and application requirements and are installed using many different techniques such as standard welding and drill and tap techniques. Other methods and techniques may include making the fitting an integral part of the substrate workpiece structure.
Integral fittings made part of another structure are, generally, completed in the original machining and fabrication process and are, generally, designed to meet the needs of equipment for which the fitting is integral with. However, most applications for fittings are installations that are separate from the manufacturing of the substrate equipment and generally completed in the field or in an industrial plant. There are many such applications where a fitting, stud or other apparatus is attached to a substrate such as a tank, plate, valve or some other type substrate workpiece.
Fittings installed by drilling and tapping methods result, first, in a threaded hole and then, second, turning a threaded fitting in, to be secured in that threaded hole. This achieves at least two objectives: (1) a fitting is installed to be used for a specific purpose; and (2) a hole exists where the threads were tapped.
Some of the disadvantages of the drill and tap method for the above options include, but are not limited to: (1) there are concerns for drilling a hole in a pressure vessel where the drill hole is exposed to the atmosphere during and after the operation; (2) there are concerns for drilling into a vessel with liquid inside, where the drilled hole is exposed to the atmosphere during and after the operation; (3) drilling a hole is a separate operation and requires separate tools and operation time: (4) tapping threads after drilling the holes requires time and tools: (5) the drilled hole to accommodate the tap may be larger than permitted or required; (6) tapped holes are not strong when compared to the substrate material; (7) tapped holes may not be easily completed in certain substrate materials, where the tap cannot be effectively utilized; (8) tapping under pressure conditions can be hazardous; (9) tapping holes with liquid in the area could be difficult and hazardous; and (10) threaded fittings are subject to leakage when installed and after a time period of use.
To give another illustration of installing fittings which require a connecting hole, there are many applications where a fitting, stud or other apparatus is attached to a substrate, such as a tank, plate, valve or some other type substrate workpiece, by standard or automatic welding procedures. The joining of materials to form a strong cohesive, high strength, fine grain weld bond is common to industry throughout the world. It is commonly achieved by arc welding, o-xyfule gas welding, flash welding, brazing, soldering, electron beam welding, laser beam welding and other techniques where open flame does not present an explosive hazard. In most cases, the exposed flame or arc creates no hazard and is practical to use. In addition to the explosive hazard, another concern is the bonding of dissimilar materials.
Fittings are installed by first welding a fitting at a pre-selected location and then, drilling a hole through the fitting and into the substrate. This achieves two objectives: (1) a fitting is installed to be used for a specific purpose and is securely in place; (2) a hole can then be drilled with the fitting in place; and (3) there are no threads to permit liquids or gas to leak. Some of the disadvantages of the standard weld and drill method described above include, but are not limited to: (1) welding introduces significant heat to the general area of the substrate and depending on the application, the heat may not be acceptable; (2) welding techniques require a certified and qualified weld technician to assure good bonding and safe procedures; (3) welding cannot be completed unless there is adequate room for covering all areas of the fitting; (4) in areas where combustible gases are present, it is not usually possible to use an open flame or arc welding procedure, due to the attendant danger of fire or explosion; (5) some materials, such as stainless steel, will not easily bond with aluminum alloys using the aforementioned welding processes; (6) there are concerns for drilling a hole in a pressure vessel where the drill hole is exposed to the atmosphere during and after the operation; (7) there are concerns for drilling into a vessel with liquid inside, where the drill hole is exposed to the atmosphere during and after the operation; (8) drilling a hole is a separate operation and requires separate tools and operation time; (9) the drilled hole, to accommodate the tap, may be larger than permitted or required; (10) welding fittings to pressure vessels or lines can be hazardous; (11) welding holes to vessels or lines with liquid could be hazardous and cause poor weld conditions; (12) surface preparation requires time and expense; and (13) the process is lengthy and cumbersome.
One solution to the above-outlined problems is the friction weld procedure, which achieves a fusion bond when installing fittings which require a connecting hole, in an application where a fitting, stud or other apparatus is attached to a substrate such as a tank, plate, valve or some other type substrate workpiece. The friction welding fusion bonding process and its related processes rely on friction heat generation between surfaces to provide a material flux which may be forged to produce an integral bond between the surfaces. In the friction welding process, relative rotation between a pair of workpieces (i.e., the two pieces to be welded together, a rotatable workpiece and a stationary substrate workpiece) is caused while the workpieces are urged together. All friction welders have a means of holding the rotatable workpiece (fittings of various types) in a collet type device. Some collets hold the workpiece by mechanically tightening and clamping against the workpiece, other collets hold the workpiece by threads, still others have a slip-and lock arrangement, either direct mechanical linkage or by some sort of centrifugal clamping mechanism, which tightens up against the workpiece when rotation begins, and other collets have various geometries to hold the rotatable workpiece during the friction welding process.
In conventional friction welding, the rotatable workpiece (fitting) is attached in the collet of a motor driven unit and rotated at a predetermined speed, while the other stationary workpiece is maintained in a fixed, stationary orientation. When the appropriate rotational speed is reached, the two workpieces are brought together and an axial force is applied. Heat is generated as a result of the friction generated by the interface of the respective surfaces, which continues for a predetermined time or until a preset amount of upset takes place. Thereafter, the rotational driving force is discontinued and the rotation of the rotatable workpiece is stopped. The axial force between the two members is maintained or increased, however, for a predetermined period of time to finalize the weld. The rotatable workpiece can be cylindrical, rectangular, square, curved or other geometric configuration such as a stud or shaft. The stationary workpiece can also be rectangular, square, curved or other geometric configuration such as a tank, pipe, other fitting, line or other configuration requiring a fitting with a through hole.
Further describing the friction weld process, after the friction welding process has started, on initial contact of the welding surfaces, there is a "burn-off" phase which removes foreign materials from contact area of both workpieces, The "burn-off" phase, is immediately followed, in an outward radial direction, by an "upset" phase where specific contact areas of both workpieces are turned to a plastic condition, causing the establishment of a flux of hot metal due to the relative rotation and high axial pressure urging the two workpieces together, caused by resistive friction between the workpieces. After automatic or operator shutdown of the rotation of the rotatable workpiece, there is a "forging" phase where axial pressure is maintained between the workpieces until the plastisized material cools and the weld fuses during "fusion bonding" phase.
The advantages of the friction welding process include, but are not limited to: (1) flux and shielding gas are not required; (2) in most cases, the weld strength is as strong as or stronger than the weaker of the two materials being joined; (3) surface cleanliness is not as significant, compared with other welding processes, since friction welding tends to disrupt and displace surface films; (4) there are narrow heat-affected zones; (5) the process is generally environmentally clean; (6) friction welding is suitable for welding most engineering materials and is well suited for joining many dissimilar metal combinations; (7) no filler material is needed; (8) operators are not required to have manual welding skills; (9) the process is easily automated for mass production; and (10) welds are made rapidly compared to other welding processes.
Friction welding has been used in the past to install fittings in such applications where a fitting, stud or other apparatus is attached to a substrate such as a tank, plate, pipes, lines, valve or other type substrate workpiece, in an industrial or commercial application, and a through hole would be part of the requirements. The fitting is first fused to the substrate workpiece and, then, the hole is drilled, axially through the fitting, as a second operation after the friction welded fitting is fused to the substrate workpiece. Some of the disadvantages include, but are not limited to: (1) there are concerns for drilling a hole in a pressure vessel where the drill hole is exposed to the atmosphere during and after the operation; (2) there are concerns for drilling into a vessel with liquid inside, where the drilled hole is exposed to the atmosphere during and after the operation; and (3) drilling a hole is a separate operation and requires separate tools and operation time.
One solution to the above-outlined problems is the "friction welder drill and fuse fitting apparatus", the subject of this invention. While this invention does not describe a new concept in a friction welding machine apparatus or a new concept in holding the friction welding rotatable fitting (bolt, stud, shaft, or etc.) with a collett, it does, however, present a unique and novel concept and method whereas a drill bit geometry can be made an integral part or attachment to a rotatable friction welding fitting, so as to permit the drilling of a hole in a substrate workpiece and fusing a friction welding fitting, in line over that hole, in one set-up operation. The friction welder drill and fuse fitting apparatus can also be made an integral part or attachment to the substrate workpiece.
The advantages of the friction welder drill and fuse fitting apparatus include, but are not limited to: (1) maximum fusion bonding and weld strength can be achieved to and, in some cases, beyond the diameter of a standard fitting; (2) greater strength is achieved with the friction welder drill and fuse fitting apparatus; (3) the fusion of the fitting to the substrate and the drilling of the hole is accomplished in one operation; (4) provisions can be made to provide sealing, while drilling and fusing a fitting to a substrate that is pressurized; (5) provisions can be made to provide sealing while drilling and fusing a fitting to a substrate that contains liquid; (6) the drill and fuse technique and method is simple and consumes less time than above described methods; (7) a fusion seal, or other type sealing means, can effectively block gas or liquid when friction welding a drill and fuse fitting apparatus to a tank, line or other object containing gas or liquid, prior to the drill bit breaking through the substrate workpiece; and (8) valves, seals, caps, plugs, one way valves or other components, to maintain pressure and leak tight conditions, during and after the fitting is installed, can be adapted to, or integral to a drill and fuse fitting, thus permitting access to and through the fitting at a later time.
Thus, while friction welding of fittings to substrates has met with general acceptance in industry in the friction welding installation of fasteners and other components, there has been a need in the art for installing a fitting and drilling a hole for access through that fitting with a through hole in a single set-up operation.
There has been an additional need in the art for friction welding installation of a fitting and drilling a hole for access through that fitting in a single set-up operation, without the concern for liquids or pressurized gases contained in a substrate vessel.
There has also been a need in the art for friction welding installation of a fitting and drilling a hole for access through that fitting in a single set-up operation, whereas another fitting, pipe, line or other component can be attached after the fitting has been installed. There has been an additional need in the art for friction welding installation of a fitting and drilling a hole for access through that fitting in a single set-up operation, where that drilled hole can be effectively blocked by a cap, plug, valve or other device until later used to connect piping, instrumentation, fittings and other connectors, without the concern for pressure or liquid contained in a substrate vessel.